.arrow span{
    position: absolute;
    width: 50px;
    height: 50px;
    color: #fff;
    text-align: center;
    line-height: 50px;
    display: none;
    background-color: rgba(0,0,0,.4);
    top: 50%;
    cursor: pointer;
    transform: translateY(-50%);
}

.arrow span:hover{
    background-color: rgba(0,0,0,.7);
}

.arrow .left{
    left: -10px;
    border-radius: 0 25px 25px 0;
}

.arrow .right{
    right: -10px;
    border-radius: 25px 0 0 25px;
}
